1. Field of the Invention
The present invention relates to an indexable insert and a drill (indexable drill) in which a plurality of indexable inserts are combined to define cutting edges.
2. Description of the Related Art
Drills used for drilling holes in a metal workpiece include a drill with its cutting edges defined by a plurality of indexable inserts (hereinafter, also merely referred to as inserts). Such a drill is disclosed in the following references and the like.
Japanese Registered Utility Model No. 2582812 discloses an indexable insert for a drill, and a drill with its cutting edges defined by the inserts. In the configuration, a chip breaker is improved to smoothly dispose chips. Also, Japanese Unexamined Patent Application Publication No. 2002-307221 discloses an indexable insert for a drill with all around type breakers having breaker grooves in a rake face entirely along cutting edges. The Publication also discloses an indexable insert additionally having protrusions (protruding portions) in the breaker grooves.
Also, there are suggested an indexable insert (with the all around type breakers) having breaker walls along the cutting edges, instead of the breaker grooves, and an indexable insert having small breaker protrusions separately provided at the rake face. The indexable inserts with the all around type breakers may contain grooves that locally increase chip flow-out resistance to increase chip disposability (parting performance).
In the indexable inserts disclosed in the above-mentioned references and the like, each chip breaker efficiently applies warp to the flow-out chips, thereby efficiently disposing the chips. However, since the contact area of the chips to the surface of the chip breaker is increased, the chip flow-out resistance and the cutting resistance may be increased.
Like problems may appear in the insert with the all around type breakers additionally having the grooves. In this kind of indexable insert, the chip flow-out resistance may be locally increased because of the grooves, and hence, the cutting resistance is further increased.
In the indexable insert having the small protrusions separately provided as the breakers, the chip flow-out resistance and the cutting resistance may be reduced. However, since the chips come into contact with the small protrusions by point contact. Thus, the advantageous effect of the chip breaker may be reduced, and the chip disposability may deteriorate.